Safety control unit, safety control method, and safety control program

Abstract

A safety control unit includes: a memory; a computation control part; and an input and output unit for connecting the computation control part to a safety input device and an output device to be safely controlled. A system program includes a data refresh program for executing a data refresh of safety control data of the safety input device and the output device and the control data of the memory via the input and output unit. If the computation control part receives a change of a control program, the computation control part stops executing the control program. The computation control part executes the change of the control program while executing a part of the system program including the data refresh. The computation control part resumes executing the control program.

The invention claimed is: 
     
       1. A safety control unit comprising:
 a memory that stores a system program for safety control, a control program for safety control comprising a sequence command computation program and a user program, and control data; and 
 a computation control part configured to execute safety control using the control data, the system program, the sequence command computation program, and the user program; and 
 an input and output unit connecting the computation control part to a safety input device and an output device to be safely controlled, wherein 
 the system program comprises a data refresh program for executing a data refresh for safety control comprising: refreshing safety input data in the control data stored in the memory via the safety input device; and outputting safety computation results via the output device, and 
 the computation control part is configured by programming to perform operations comprising:
 receiving a change of the sequence command computation program or a change of the user program; 
 determining whether a safety control continuation setting is set; and 
 in response to determining that the safety control continuation setting is set:
 stopping execution of the sequence command computation program and the user program in response to receiving the change of the sequence command computation program or the user program while continuing to execute the data refresh program; 
 
 unloading the sequence command computation program and the user program from the memory; 
 loading, to the memory, the sequence command program and the user program including the change of the sequence command computation program or the user program while continuing to execute the data refresh program; and
 resuming execution of the sequence command computation program and the user program including the change of the sequence command program or the user program while continuing to execute the data refresh program. 
 
 
 
     
     
       2. The safety control unit according to  claim 1 , wherein the computation control part is further configured by the programming to perform operations further comprising, in response to receiving the change of the sequence command computation program or the change of the user program and determining that the safety control continuation setting is not set:
 stopping execution of the data refresh program; 
 stopping execution of the sequence command computation program and the user program; 
 unloading the sequence command computation program and the user program from the memory; 
 loading, to the memory, the sequence command computation program and the user program including the change of the sequence command computation program or the user program; and 
 resuming execution of the sequence command computation program and the user program including the change of the sequence command computation program or the user program and resuming execution of the data refresh program. 
 
     
     
       3. A safety control method, comprising:
 storing, in a memory, a system program for safety control, a control program for safety control comprising a sequence command computation program and a user program, and control data; 
 executing safety control using the control data, the system program, the sequence command computation program, and the user program; 
 executing a data refresh program, included in the system program, for executing a data refresh for safety control comprising: refreshing safety input data in the control data stored in the memory; and outputting safety computation results; 
 receiving a change of the sequence command computation program or a change of the user program; 
 determining whether a safety control continuation setting is set; and 
 in response to determining that the safety control continuation setting is set:
 stopping execution of the sequence command computation program and the user program in response to receiving the change of the sequence command computation program or the user program while continuing to execute the data refresh program; 
 unloading the sequence command computation program and the user program from the memory; 
 loading, to the memory, the sequence command computation program and the user program including the change of the sequence command computation program or the user program while continuing to execute the data refresh program; and 
 resuming execution of the sequence command computation program and the user program including the change of the sequence command computation program and the user program while continuing to execute the data refresh program. 
 
 
     
     
       4. A non-transitory computer-readable storage medium storing a safety control program, which when read and executed causes a computation control part to execute operations comprising:
 storing, in a memory, a system program for safety control, a control program for safety control comprising a sequence command computation program and a user program, and control data; 
 executing safety control using the control data, the system program, the sequence command computation program, and the user program; 
 executing a data refresh program, included in the system program, for executing a data refresh for safety control comprising: refreshing safety input data in the control data stored in the memory; and outputting safety computation results; 
 receiving a change of the sequence command computation program or a change of the user program; 
 determining whether a safety control continuation setting is set; and 
 in response to determining that the safety control continuation setting is set:
 stopping execution of the sequence command computation program and the user program in response to receiving the change of the sequence command computation program or the user program while continuing to execute the data refresh program; 
 unloading the sequence command computation program and the user program from the memory; 
 loading, to the memory, the sequence command computation program and the user program including the change of the sequence command computation program or the user program while continuing to execute the data refresh program; and 
 resuming execution of the sequence command computation program and the user program including the change of the sequence command computation program and the user program while continuing to execute the data refresh program. 
 
 
     
     
       5. The method according to  claim 3 , further comprising:
 in response to receiving the change of the sequence command control program or the user program program and determining that the safety control continuation setting is not set: 
 stopping execution of the data refresh program; 
 stopping execution of the sequence command computation program and the user program; 
 unloading the sequence command computation program and the user program from the memory; 
 loading, to the memory, the sequence command computation program and the user program including the change of the sequence command computation program or the user program; and 
 resuming execution of the sequence command computation program and the user program including the change of the sequence command computation program or the user program and resuming execution of the data refresh program.